The group, spearheaded by independent MEP Steven Woolfe, has questioned the “appropriateness” of the Frenchman meeting a slew of high-profile europhiles including Nick Clegg and Jeremy Corbyn.
Brexiteers reacted with fury today as Mr Barnier agreed to meet a delegation fronted by the former Lib Dem leader which also included veteran Remainers Ken Clarke and Andrew Adonis.
They accused the trio of deliberately trying to undermine Theresa May’s negotiating position in a desperate bid to keep Britain in the EU and said the Frenchman should have refused to host them.
In an explosive letter, Mr Woolfe warns him: “I fear that today’s meeting could jeopardise the negotiations as well as the possibility of the UK and the EU reaching a deal that would benefit both sides.”
EU chief negotiator Michel Barnier & Steven Woolfe
British MEP Steven Woolfe
Mr Woolfe has written a letter demanding a meeting with Mr Barnier
Their visit caused particular surprise and consternation as Mr Clarke is a backbencher and Lord Adonis a peripheral figure within Labour, whilst Mr Clegg no longer holds any official position having lost his seat in June.
Mr Barnier has also recently met with Mr Corbyn, the Labour leader, whilst the EU Commission president Jean-Claude Juncker has greeted Tony Blair in Brussels twice this year alone.
In a letter to the chief negotiator, seen by express.co.uk, Mr Woolfe warns eurocrats that by exclusively meeting europhiles they risk “a perception that you are holding secondary, parallel and unofficial discussions”.
The independent MEP has previously warned this website that there is a “Remainer coup” underway with senior pro-EU politicians using their influence in Brussels and Westminster to undermine top Brexiteers.
And last week it emerged that influential Tories are plotting to go over Mrs May’s head and hold direct talks with Brussels in a bid to steer the UK towards a softer Brexit inside the single market.
In his letter, Mr Woolfe writes: “As you will be aware, Mr Clegg, Mr Clarke and Lord Adonis do not hold any official, representative position to the UK Government. In addition to this, Mr Clegg no longer holds any elected position in the UK at all, and is in fact a private citizen.
“By meeting with these individuals, there is a risk that a perception develops that you are holding secondary, parallel and unofficial discussions with individuals outside of the UK Government.
“It is widely known that Mr Clegg, Mr Clarke and Lord Adonis have very different positions to the UK Government on its negotiating position, and have at times been openly critical of the Government’s policy.
“As a result, the risk of a perception developing that you are establishing secondary backchannels around the Government is significantly higher than you having met with other individuals.”
I fear that today’s meeting could jeopardise the negotiations
Mr Woolfe warns him that Britain there is “a public fear that these individuals are driven to undermine the negotiation process itself” and calls on him to publish full details of his meeting with the three europhiles.
He also urges the Frenchman to “provide details on the criteria that you use to accept meetings”, given that so far the Commission has overwhelmingly hosted pro-EU figures.
The British MEP says that a “perception has sadly developed that certain members of the UK political community have had access to you that could jeopardise the balance of the [Brexit] process”.
And he calls on Mr Barnier to agree to meet a “delegation of individuals who campaigned for Leave”, saying this would help to allay concerns that Remainers are getting unfair levels of access in Brussels.
1 of 12
He writes: “This would go a long way to restoring the perception that you are not building a secondary backchannel with members of the UK political who have a certain, selective view on the EU-UK negotiations.”
The Commission boss, Mr Juncker, did recently meet with Ukip MEP David Coburn at his Berlaymont office in a rare example of a top EU figure hosting a prominent British eurosceptic.
Defending today’s meeting between Mr Barnier and the three europhiles – who jokingly referred to themselves as “the rebels”, an EU Commission spokesman said it was Mr Clegg and his company who requested the get-together.
He added: “Michel Barnier’s door is always open for people who want to speak to him and his team across the political spectrum and from all walks of life all walks of parties.
“There is a negotiating process. On one side is David Davis and on the European side is the chief negotiator of the EU Michel Barnier, nobody else.”